Field of the Invention
The present invention relates to an image forming apparatus, such as an electrophotographic copying machine and an electrophotographic printer.
Description of the Related Art
Conventionally, in image forming apparatus using electrophotographic technology, a toner image formed on a photosensitive drum is transferred to a recording medium, so that an image is formed on the recording medium. Some such image forming apparatus are provided with a cleaning apparatus configured to collect residual toner remaining on the photosensitive drum after the toner image is transferred. The cleaning apparatus includes a cleaning member as a contact member configured to remove residual toner on the photosensitive drum, a collection container configured to store the residual toner therein, and a collection sheet member configured to prevent the residual toner in the collection container from leaking to the outside of the collection container.
Conventionally, “abnormal noise” may be generated from the cleaning apparatus. Abnormal noise is caused when consumption of a photosensitive drum and a developing apparatus progresses and the friction coefficient μ of the surface of the photosensitive drum increases. If the friction coefficient μ of the surface of the photosensitive drum increases, the cleaning member easily causes stick-slip, and when vibration of the cleaning member is transferred to the collection container, the vibration resonates with the natural frequency of the collection container to generate abnormal noise. The stick-slip as used herein refers to self-excited vibration caused when friction surfaces repeatedly adhere and slide on each other. To suppress abnormal noise, the friction coefficient μ of the surface of the photosensitive drum needs to be maintained low until the life of the photosensitive drum reaches the last stage since the start of the use of the photosensitive drum.
The generation of such abnormal noise is undesirable for users who use image forming apparatus in office environments. In Japanese Patent Application Publication No. H04-245285, a coating layer containing lubricant particles is provided at a part of a collection sheet member that contacts with a photosensitive drum. In this manner, the lubricant particles are supplied from the collection sheet to the surface of the photosensitive drum to decrease the friction coefficient μ of the surface of the photosensitive drum. By decreasing the friction coefficient μ of the surface of the photosensitive drum, abnormal noise caused due to vibration of a cleaning member is suppressed.